In those motor vehicles having an engine air inlet duct or passage formed by and between the engine compartment hood and an inner panel, the practice has been to arrange the duct so as to direct cold air from the windshield area to the inlet of an air cleaner assembly mounted within the engine compartment and on which the hood duct seals when the hood is closed. In addition to the desirably cold air, the hood duct provides water separation by inertia and the hood may be lifted to provide service to the air filter with the air filter then being sealed even when the hood is open. Typically, the air cleaner assembly is mounted on the engine's carburetor or throttle body in the case of fuel injection and/or diesel engine or is packaged remotely and plumbed to the engine's intake system. In addition, a mass air flow sensor may be a part of the air cleaner system. But in either case, there has heretofore been nothing to add any significant acoustical impedance to the system to help attenuate the noise that can be generated with such a hood duct.